As the developers of Open Journal Systems, Open Conference Systems, Open Harvester Systems, and Open Monograph Press, the PKP team are experts in helping journal managers and conference organizers make the most of their online publishing projects. PKP Publishing Services offers support for:

As a customer of PKP Publishing Services, you will not only receive direct, personalized support from the PKP Development Team, but will be contributing to the ongoing development of the PKP applications. All funds raised by PKP Publishing Services go directly toward enhancing our free, open source software. For more information, please contact us.

However, as I try to add the archive, I get error claiming that my URL is invalid.

I am by no means a web application programmer (rather a C/C++ developer) but I dug a little and here is what I found:

The actual http-request is generated here: lib\pkp\classes\file\wrappers\HTTPFileWrapper.inc --> open(). The problem is that if SSL is used (https) harvester includes the protocol identifier to the request Host-field. And this seems to be wrong and causing servers to respond with "Bad Request, 400". I verified the behaviour also by simple request to www.example.com.

Fix for me was a little hack removing the ssl:// - prefix from the generated request. So final request should have the Host-field like this: "ao.doria.fi". Instead of "ssl://ao.doria.fi", which is causing server to reply "Bad Request".

I am using version 2.3.0.

As I said, I'm no web application developer so I might be doing something silly, but I thought to report this finding anyways

Without the ssl:// prefix, you're not using SSL as a transport for the data -- it'll go through plain HTTP that way. You might try turning off the "allow_url_fopen" in config.inc.php, but in general, it would help to check the repository's log to find out what it's seeing of these requests.